Hi,
I have a relatively old CB installation (1.2.3) on a Joomla 1.5.18
After moving to a new server I ran into the following problem:

The User management tab gives me the following error message with Chrome (with Safari an empty page is shown)

The website encountered an error while retrieving http://.../administrator/index.php?option=com_comprofiler&task=showusers. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

using the Tools I get the same result when I try to:
Synchronize users
Check Community Builder User Fields Database

all the other tools are 'green' except for one error message:
Warning: 1 entries in users table without corresponding comprofiler table rows.

users id: 270 are missing in comprofiler table

This one can be fixed using menu Components-> Community Builder-> tools and then click `Synchronize users`.

which does not really help, because I can not synchronize ...

any hints on how to solve this are appreciated!
thanks
m